To everyone who's concerned about their PR card still in progress...
I was just as worried when I found that I wouldn't be able to get my PR card for my trip to Europe. I landed on April 22nd, and thought my PR card should be arriving in the first week of June, where there's one more week before my scheduled flight to Europe. As it turned out, after two weeks being in Europe, and it is still not here!
So here's my recent story (June 2015) of getting back from overseas without my PR card and holding a passport that is not from any visa-exempt country - I hold a Chinese passport. I have a student visa to begin with (valid till August this year), and when I was flying from Athens to Paris and Paris back to YVR, there are two check points that I was asked about my status in Canada. Like many of you mentioned here, the problem is not with the Canadian boarder, because you have the RIGHT to enter Canada when you are a Canadian PR, and the boarder officers know it. Heck, they should be able to find your information in their system anyway if they don't believe your landing confirmation paper. The only problem is with the airline, who because they have no way of verifying your status in Canada, would not gamble to take you on the plane and risk having to ship you out of Canada if the Canadian boarder do not admit you. So when the airline company people asked me in Athens to find my visa, I showed them my student visa, which is of course invalid, and my study permit was taken off by the boarder officer when I landed. They were ok with that. Then in Paris, when they checked again before I board the plane, they flipped through my passport, and found that I have the PR confirmation paper. So they asked if I have my PR card, to which I simply replied "no... because they just haven't sent it to me." It may be pure luck, but the airline boarding people just laughed and let me on. Back in YVR, I lined up in the PR line, and asked the information people where to go if I don't have my PR card yet. They simply direct to another line - quite possibly for people coming to land - and the boarder officer just let me through after I mentioned I haven't received my PR card, so I have to go through an agent checkpoint.
My point is, as long as you still have a Canadian visa that is shown to be valid (even though it may not be since you've already landed), I would think it is a safe bet for you to get on a flight and back. There is of course certain risk in doing that, and different airline may have different policies (I flew with Air France), but there is really no consequence in telling the airline one way or another how you're going to get admitted into Canada. Once you're at the Canadian boarder, you can relax a bit, because worst comes to worst, they question you for some time, but you know you will be let in as it is a RIGHT that you've earned as a PR, not a privilege. The boarder officers do not seem to care one way or another, and with the growing processing time non-sense for PR card, I believe many of them would understand it. For example, I drove to the US for gas every month, and they kept asking if I have my PR card. A few days ago when I drove south of the boarder for some letters. On my way back, one boarder officer finally said "You should probably give them a call to see what's going on after over 2 months, just to be sure they don't send it to the wrong address." And when I told him about the processing time, he stuck his tongue out and made a face... So yea, always remember, Canadians are polite, understanding, and easier to deal with - one of the many reasons I want to immigrate to Canada to begin with.